PSAT Math : Arithmetic

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #131 : Arithmetic

Alternating1

Possible Answers:

\dpi{100} -\frac{47}{60}

\dpi{100} \frac{47}{60}

\dpi{100} \frac{17}{60}

\dpi{100} \frac{43}{60}

\dpi{100} -\frac{43}{60}

Correct answer:

\dpi{100} \frac{47}{60}

Explanation:

Alternating2

Alternating3

Example Question #1 : How To Add Fractions

Solve \frac{3}{7}+\frac{5}{8}-\frac{1}{2}.

Possible Answers:

\frac{33}{56}

\frac{31}{56}

\frac{7}{8}

\frac{5}{7}

Correct answer:

\frac{31}{56}

Explanation:

Finding the common denominator yields \frac{24}{56}+\frac{35}{56}-\frac{28}{56}. We can then evaluate leaving \frac{31}{56}.

Example Question #2 : How To Add Fractions

What is the solution, reduced to its simplest form, for x = \frac{7}{9}+\frac{3}{5}+\frac{2}{15}+\frac{7}{45}} ?

Possible Answers:

x = \frac{7}{15}

x = \frac{5}{3}

x = \frac{75}{45}

x =2

x = \frac{115}{45}

Correct answer:

x = \frac{5}{3}

Explanation:

x=\frac{7}{9}+\frac{3}{5}+\frac{2}{15}+\frac{7}{45}=\frac{35}{45}+\frac{27}{45}+\frac{6}{45}+\frac{7}{45}=\frac{75}{45}=\frac{5}{3}

Example Question #3 : How To Add Fractions

What is the sum of  and ?

Possible Answers:

Correct answer:

Explanation:

We can begin by eliminating the obviously wrong answers. We know that the sum of the two fractions will be more than 1, so the answer choices  and  are out. Now, let's add the two fractions:

Begin by converting  to .

Now find the common denominator of  and . The least common multiple of 5 and 6 is 30, so 30 is the common denominator. Now alter both fractions so that they use the common denominator:

 

Now we can easily add the two fractions together:

The answer is .

Example Question #1 : How To Find The Reciprocal Of A Fraction

What is the reciprocal of the following fraction: 18/27

Possible Answers:

27/18

9/27

9

-18/27

Correct answer:

27/18

Explanation:

A fraction multiplied by its reciprocal will equal 1. To find the reciprocal of a fraction, switch the denominator and numerator. The reciprocal of 18/27 is 27/18.

Example Question #1 : How To Find The Lowest / Least Common Denominator

3/5 + 4/7 – 1/3 =

Possible Answers:

3/37

7/9

88/105

4/3

72/89

Correct answer:

88/105

Explanation:

We need to find a common denominator to add and subtract these fractions. Let's do the addition first. The lowest common denominator of 5 and 7 is 5 * 7 = 35, so 3/5 + 4/7 = 21/35 + 20/35 = 41/35. 

Now to the subtraction. The lowest common denominator of 35 and 3 is 35 * 3 = 105, so altogether, 3/5 + 4/7 – 1/3 = 41/35 – 1/3 = 123/105 – 35/105 = 88/105. This does not simplify and is therefore the correct answer.

Example Question #131 : Fractions

3/5 + 4/7 – 1/3 = 

Possible Answers:

88/105

3/37

72/89

7/9

4/3

Correct answer:

88/105

Explanation:

We need to find a common denominator to add and subtract these fractions. Let's do the addition first. The lowest common denominator of 5 and 7 is 5 * 7 = 35, so 3/5 + 4/7 = 21/35 + 20/35 = 41/35. 

Now to the subtraction. The lowest common denominator of 35 and 3 is 35 * 3 = 105, so altogether, 3/5 + 4/7 – 1/3 = 41/35 – 1/3 = 123/105 – 35/105 = 88/105. This does not simplify and is therefore the correct answer.

Example Question #1 : How To Find The Lowest / Least Common Denominator

Possible Answers:

Correct answer:

Explanation:

Example Question #1 : How To Find The Lowest / Least Common Denominator

Simplify:

Possible Answers:

Correct answer:

Explanation:

First, find the common denominator of the fractions in order to add them together. Looking at the first two fractions, we can see that the common denominator is 15 because 3 times five is 15. We can now change both fractions to have a denominator of 15 so that we can add them together:

Now, find a common denominator for the remaining fractions. This can be done by listing multiples of 15 and 20 and finding the lowest common multiple:

15: 15, 30, 45, 60, 75

20: 20, 40, 60, 80

60 is the lowest common multiple, so it is our least common denominator.

Example Question #1 : How To Find A Solution To A Compound Fraction

Simplify:

Possible Answers:

Correct answer:

Explanation:

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